External corner lighting is desirable so that a light mounted on a corner can illuminate evenly, typically in the 270.degree. arc around an exterior right angled corner. Another requirement is that the light generating lamp, bulb or tube be easily changeable. This is most easily done by having the canister removable from the corner, otherwise the canister must be taken apart in place, which is generally inconvenient. By having mounting brackets attached around the corner and detachably mounting the canister thereon, the canister is made removable. A vertical groove enables the canister to fit the corner more snugly and thus reduces any play caused by wind and weather. Hooks mounted within the canister grooves engage gaps formed between corner and mounting brackets. The close symmetrical mounting of the canister on the corner provides photometrically even lighting from the light or luminaire.